Laser printers and ink jet printers have a toner or ink cartridge. Usually, sensors are employed to detected when a cartridge is empty. In this case, either an indicator on the printer notifies the user that the cartridge is empty, or a respective message is sent back to the computer or network to which the printer is connected.
Various approaches are known which provide for a precise determination of the amount of toner to be used in a xerographic system, for example. According to U.S. Pat. No. 3,409,901, M. H. Dost et al., filed Jul. 13, 1967, for instance, the beam current for a cathode ray tube used in a xerographic system is integrated to estimate the toner concentration needed in the system.
In U.S. Pat. No. 4,468,112, Suzuki et al., filed Feb. 11, 1982, constant optimum image density is achieved in an electrographic copier by employing appropriate detectors which determine the image density and based on that the amount of toner to be fed to the developer.
Methods for continuously monitoring toner depletion from a development station is described in U.S. Pat. No. 3,529,546, Kollar which issued September 1967, and U.S. Pat. No. 4,413,264, A. S. Cruz-Uribe et al., filed Jan. 11, 1982. The replenishing rate is adjusted in response to the number of character print signals (e.g. pixel signals) applied to the print head.
Another approach for the determination of toner depletion from the developer mixture is addressed in U.S. Pat. No. 5,204,698, LeSueur et al., filed Aug. 27, 1992.
There is a need for remotely detecting and monitoring the toner or ink usage on-the-fly in a flexible and cost-effective manner. This would help to better manage resources and to make decision before or while a print job is executed.
It is an object of the invention to provide an apparatus or method which keeps track of the amount of toner or ink used in a printer since the toner or ink has been refilled or the cartridge has been replaced.
It is another object to provide immediate feedback to the user or operator as to how much toner or ink will be required for a particular print job.
It is a further object to provide for an indication if the toner or ink cartridge is expected to be empty.
It also is an object to determine the cost of a particular print job taking into consideration not only the number of pages, but also the amount toner or ink required.